A COMPARISON OF IN VIVO AND IN VITRO STATHMOKINETIC METHODS FOR THE STUDY OF CELL PROLIFERATION IN HAMSTER ORAL EPITHELIA

Mitotic indices (MI) expressed as numbers of metaphase fingers per 100 basal cells in the cheek pouch and palatal epithelium of the Syrian hamster following metaphase arrest with vinblastine sulphate (VLB) were compared using in vivo and in vitro techniques. The MI in vivo 4 1/2 hr after intraperitoneal injection of 4 mg VLB/kg body weight 2.69 +/- 0.37 for check pouch and 12.08 +/- 1.09 for palate. MI in vitro was measured using small tissue explants cultured for 4 hr in medium supplemented with VLB at concentrations ranging from 6-600 micrograms/ml. The maximum MI for cheek pouch epithelium in vitro (2.7) did not differ signficantly from that observed in vivo (P > 0.50) and was obtained in the presence of 12-30 micrograms VLB/ml, a concentration comparable with that used in vivo. In contrast, the maximum MI for palate epithelium in culture (5.6) was significantly lower than that in vivo (P < 0.001) and was only achieved in the presence of extremely high concentrations of VLB. Possible reasons are discussed for the discrepancy between the MI for palatal epithelium in vivo and in vitro.